Vehicles employ fans that are powered by electric motors to move air as part of cooling systems. Known electric motors for fans may employ pulsewidth-modulated control to control the fan speed. During high-way cruising conditions, the electric motor may be switched off when sufficient ram air is available to maintain engine coolant temperature within predetermined limits. However, ambient airflow across the fan may cause it to rotate. Such operation may deflect airflow, and the fan and electric motor may operate as a generator. Known systems may employ a blocking diode in series with a DC power bus of a drive circuit for the electric motor to prevent back-feeding of electric power onto the DC power bus. Back-feeding of electric power is due to the induced voltage in the motor windings (often referred to as back-electromotive force, or back-EMF) exceeding the voltage applied to the motor controller DC input. Use of a blocking diode may result in overvoltage at the electric drive terminals under certain operating conditions, e.g., highway vehicle speeds, due to back-EMF that is generated by a windmill effect on the electric motor. Furthermore, use of a blocking diode on the DC power bus may cause conduction losses and reduce system efficiency.